Cancer patients often experience mental anguish and stress, but a single dose of a hallucinogen found in psychedelic mushrooms, along with psychological counseling, improved their mindset, two studies said Thursday.

The approach "significantly lessens mental anguish in distressed cancer patients for months at a time," said the findings in the Journal of Psychopharmacology.

The first study, led by researchers at New York University's Langone Medical Center, involved 29 people who were given psilocybin, a naturally occurring component of so-called "magic mushrooms" that is an illegal drug in the United States.

All the people in the study had advanced cancers, whether involving the breasts, gastrointestinal tract or blood. They had also been diagnosed as suffering from serious psychological distress related to their disease.

After their treatment, 80 percent experienced lasting relief from their distress for more than six months.

A similar study by researchers at Johns Hopkins University involving 51 patients also showed big improvements in anxiety and depression.

"The most interesting and remarkable finding is that a single dose of psilocybin, which lasts four to six hours, produced enduring decreases in depression and anxiety symptoms, and this may represent a fascinating new model for treating some psychiatric conditions," said Roland Griffiths, professor of behavioral biology in the Departments of Psychiatry and Behavioral Sciences and of Neuroscience at the Johns Hopkins University School of Medicine in a statement.

Most patients said their quality of life improved, and they had more energy, better relationships with family members and were doing well at work.

"Several also reported variations of spirituality, unusual peacefulness, and increased feelings of altruism," said NYU Langone in a statement.

Among those who took part in the Johns Hopkins study, 67 percent said the experience was among the top five meaningful experiences in their lives and 83 percent reported increases in their well-being.

Perhaps even more critically, no one in the studies experience major side effects such as hospitalization, addiction or more serious mental health conditions.

"Our results represent the strongest evidence to date of a clinical benefit from psilocybin therapy, with the potential to transform care for patients with cancer-related psychological distress," said lead investigator Stephen Ross, director of substance-abuse services in psychiatry department at NYU Langone.

"If larger clinical trials prove successful, then we could ultimately have available a safe, effective, and inexpensive medication - dispensed under strict control - to alleviate the distress that increases suicide rates among cancer patients."

Griffiths points out that traditional psychotherapy offered to cancer patients, including behavioral therapy and antidepressants, can take weeks or even months to take effect and don't always work. Some of those treatments, including benzodiazepines, can become addictive.

Researchers believe that psilocybin activates parts of the brain that are influenced by serotonin, a chemical thought to play a role in mood and anxiety.

"Before beginning the study, it wasn't clear to me that this treatment would be helpful, since cancer patients may experience profound hopelessness in response to their diagnosis, which is often followed by multiple surgeries and prolonged chemotherapy," Griffiths said. "I could imagine that cancer patients would receive psilocybin, look into the existential void and come out even more fearful. However, the positive changes in attitudes, moods, and behavior that we documented in healthy volunteers were replicated in cancer patients."

Experts warned that some people should not be considered candidates for psilocybin therapy, including adolescents and those with schizophrenia.